Biosensor technology is well known in the art.
US Patent Application No. 2003/0174992 discloses a method and an apparatus for providing a zero-mode waveguide including an analyte, which is subjected to activation by electromagnetic radiation for analysing the analyte.
WO 2006/136991 entitled “Luminescence sensors using sub-wavelength apertures or slits”, discloses a biosensor with sub-wavelength spatial resolution.
WO 2007/072415 entitled “Luminiscence sensor operating in reflection mode”, discloses a method for detection of fluorescent radiation generated by molecules in an aperture.
Such a bio sensor may comprise a non-transparent material arranged on a substrate of a transparent material and forming at least one aperture for being filled with said analyte fluid. The apertures have a first in-plane dimension below the diffraction limit of the excitation light in the medium inside the apertures and a second in-plane dimension above the diffraction limit of the excitation light in the medium inside the apertures. The aperture-plane is defined by a first vector directed along the first in-plane dimension of the aperture and a second vector directed along the second in-plane dimension of the aperture. Such a wire grid has a transmission axis where light that is polarized, such that the electric field is parallel with a transmission-plane, that is defined by the first vector and a third vector that is normal to the aperture-plane, below called T polarized light, is essentially transmitted and light that is polarized such that the electric field is orthogonal to the transmission-plane, below called R polarized light, is substantially blocked.
An analyte is applied to the biosensor and penetrates into the apertures. The analyte comprises a target molecule to be analyzed. The target molecule is labeled with a luminophore and the aggregate of luminophores/target molecule is immobilized at a substrate side of the apertures while free luminophores and luminophores attached to target molecules are present at an analyte side of the apertures in the analyte. The immobilized luminophores correspond to a qualitative or quantitative representation of the target molecule to be analysed.
Emission radiation from the immobilized luminophores is determined by a detector. In order to discriminate the desired radiation of the immobilized luminophores from background radiation of the free luminphores and the target molecules labeled with a luminophores, the background radiation has to be suppressed. The background radiation may be several orders of magnitude larger than the useful radiation from the immobilized luminophores. The substantial suppression of the luminescent background radiation enables essentially background free measurements that would otherwise require rinsing, but rinsing may not take place for example during real-time measurements. For a practical wire grid biosensor illuminated with polarized excitation light, the suppression of background radiation is limited to about three orders of magnitude. This limited background suppression, ultimately results in a reduction in the accuracy and surface-specificity of the sensor. Furthermore, there is a need in the art for a biosensor that can use a non-polarized light source, such as a light emitting diode, LED, which is cheaper and may produce a larger output power.